Magnets, both permanent magnets and electromagnets, find a wide variety of uses, both practical and as entertainment devices. The poles of magnets have been named the north pole and the south pole, the north pole being the one that points northward in the Earth's magnetic field, i.e., the magnetic north-seeking pole. It is, of course, well known that like poles, i.e., two north poles, repel one another and unlike poles, i.e., a north pole and a south pole, attract one another.
This phenomenon has been used to levitate one magnet above another and offers the possibility of substantially reduced friction. Magnetic levitation of trains, for example, is one practical application of the phenomenon. However, in such a levitation application, highly sophisticated control devices are required for controlling the magnetic fields of electromagnets to overcome the inherent instabilities of the repulsion forces of two like magnetic poles. In a simple levitation system wherein one pole of a first permanent magnet is attempted to be suspended above a like pole of a second permanent magnet, the inherent instability of such a system results in the flipping over of the first magnet so that the unlike poles attract and are brought together into a stable configuration.
A number of simple levitation systems have been devised which employ specially configured permanent magnet arrangements intended to minimize the instability associated with magnetic levitation. In U.S. Pat. No. 2,323,8937 to Neal, for example, there is disclosed a magnetic system having a base magnet comprising a circular disk in which a first plurality of cylindrical magnets is disposed in a circular array about the axis of the circular disk. An upper magnet member comprising a spherical segment in which a second plurality of cylindrical magnets is disposed in a circular array of smaller diameter than the diameter of the circular array of the base magnet. The first plurality of magnets is disposed with like (north) poles and longitudinal axes directed vertically upwardly or inclined slightly toward the axis of the circular disk. The second plurality of magnets is disposed with like (north) poles and longitudinal axes directed vertically downwardly or inclined at the same inclination as the first plurality of magnets. This arrangement of the base magnet is said to produce an inverted magnetic field cone which embraces the smaller diameter magnetic field of like polarity of the upper magnet and thereby is said to stabilize the levitation system.
U.S. Pat. No. 4,382,245 to Harrigan discloses another simple magnetic levitation system which utilizes a dish-shaped lower magnet to magnetically support or levitate a magnetic top spinning coaxially above the lower magnet. The dish-shaped or concave surface of the lower magnet is said to produce radially inwardly directed lines of magnetization which, together with the gyroscopic effect of rotation of the magnetic top, provide stabilization of the levitation system. The Harrigan patent discloses another embodiment in which stabilization is said to be provided by a combination of the concave lower magnet surface and a pendulum effect resulting from a non-magnetic mass supported below the lower magnet on an arm extending from the upper magnet through a central bore in the lower magnet. Other embodiments are disclosed in which the lower field is not provided by a dish-shaped magnet but is provided by a plurality of cylindrical magnets arranged similarly to the arrangement of the aforementioned Neal patent.